In a coffee percolator of this type, the control piston moves from its brewing position directly to its flushing position, the control piston being designed in such a manner that the supply and flushing openings are opened at the same time by the action of the control means. During the brewing operation, however, a certain overpressure is generated within the brewing chamber. When the two openings are released by the control piston during its movement from the brewing position to the flushing position, this overpressure may cause water vapours to flow towards the coffee meal supply means and to condense therein, causing the coffee meal to coagulate during the following brewing cycle. It is further possible that the pressure relief through the supply opening causes coffeegrounds to be entrained in an uncontrolled manner and to accumulate at undesirable locations. Both these phenomena are highly undesirable for proper operation of the coffee percolator. In the known coffee percolator, moreover, the flushing water is only admitted after the flushing outlet has been opened.